The best way to get help here is to create a jsFiddle that demonstrates the problem. Try to make it minimal, and remove anything not directly related to the problem.

If that's not possible (for example, you are using Ajax), provide a link to your page on the Internet.

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I looked at your repo. I see you are not using:

<meta http-equiv="X-UA-Compatible" content="IE=edge" >

You should always include this to tell IE/edge to behave like a modern browser.

I also see you aren't using the recommended load sequence for jQUI. You should load in <head> not at the bottom of <body>. Loading scripts at the bottom of <body> is an old-fashioned "optimization" that seldom makes sense today.

Is there some good reason you are using window.addEventListener rather than $.on()? Are you trying to incrementally migrate your code to "vanilla Javascript"? That seems strange for a jQuery UI project, where you cannot avoid jQuery, since JQUI depends on it.